Is it Possible to Create an Opalescence Shader in Cycles?
The Problem here is that you have to use two different shaders that both use refraction rays. That makes it difficult to find a separation that lets the one shader cast rays on other objects after doing refraction and the other rays casting rays into the camera after refraction but not cast rays onto other objects.

I found this node setup to work:



Result:



Of course this is not physically correct and somewhat a hack. But with a little extra work you should be able to simulate a rather good looking opalescent shader.